This invention relates generally to nuclear reactors and, more particularly, to a gravity driven suction pump for a reactor condenser.
One known boiling water nuclear reactor includes a drywell, or containment, a wetwell, a gravity driven cooling system (GDCS) and a passive cooling containment system (PCCS). The drywell can withstand pressure generated by a reactor pressure vessel (RPV) during reactor operation, and the PCCS limits the pressure within the containment to a pressure below a selected pressure to keep the RPV core substantially cool.
Condensible and noncondensible gases exist or are generated by processes in the gas chamber of the nuclear reactor and are typically moved into the condenser. Condensible gases are condensed in the condenser. However, the capacity of the condenser degrades as the accumulation of noncondensible gases in the condenser increases.
Noncondensible gases can be removed from a condenser through vent pipes and valves controlled by automatic logic or operator action. The steam and noncondensible gases are vented to a suppression pool. The steam is condensed in the suppression pool and the noncondensible gases pass through the pool surface and accumulate in the wetwell, i.e., the air space above the suppression pool.
Alternatively noncondensible gases can be passed through a condenser by an electrical suction pump or a blower. The condenser receives steam and noncondensible gases from the drywell. The blower is connected to the condenser vent line and removes the noncondensible gases by forced air circulation from the condenser and discharges the gases back to the drywell.
In yet another alternative, vent pipes can discharge the noncondensible gases to an area of relatively lower pressure. Such venting can be employed in addition to and along with utilizing the electrical suction pump or the blower described above. The vent pipes discharge steam and noncondensible gases into the suppression pool and the wetwell.
A disadvantage of removing noncondensible gases from the condenser is that active components and operator action are required. Further, venting the noncondensible gases to an area of low pressure may result in a higher containment pressure after a postulated accident than if the noncondensible gases are evenly distributed among the drywell and the wetwell.
Accordingly, it would be desirable to provide a system for removing noncondensible gases from the condenser without active components or operator action. Additionally, it would be desirable to provide a system that enhances the circulation of condensible and noncondensible gases through the condenser and thus enhances the performance of the condenser system.